Systems of this type are known in various embodiments in the area of medical engineering. Systems are known, for example, which have a screw as a fastening means which has a cylindrical screw head on which a thread is located which has a larger diameter than the screw shaft. The thread of the screw head is a metric thread of a fine pitch. The screw shaft which is introduced into the bone tissue is likewise provided with a thread which has a larger pitch in comparison with the thread of the screw head.
In systems with screws of this type, there is a disadvantage in that compression effects occur on the tightening of the screw which are due to the fact that a thread is provided in the head region of the screw with a smaller metric pitch than at the bone thread at the shaft of the screw.
It is the object of the present disclosure to further develop a system of the initially named type such that the disadvantages known from the prior art are avoided, in particular such that compression effects do not occur.
This object is solved by a system for the fixing of bone segments or bone fragments comprising an implant plate or an implant surface plate having a bore or a cut-out with an implant screw which is guided through a bore or cut-out of the implant plate or implant surface plate (mesh). The implant screw has a screw shaft and a screw head, with the screw shaft and the screw head having threads or threaded sections which are made with identical pitches.
A fast, simple and secure solution of fastening implant screws through an implant plate or an implant surface plate (mesh) to bones and of simultaneously establishing a locking connection between the screw and the plate is made available by the system in accordance with the present disclosure. It is thus possible in a simple manner to fix bone segments or bone fragments securely in their spatial relationship to other bone parts such that a later displacement does not take place and a fast, positionally secure healing can take place.
In a preferred embodiment of the present disclosure, two components of the system, that is the screw and the plate, form a unit which is contiguous in the installed state, but which is releasable per se. In the assembled state, both components, that is the implant screw and the plate, are locked or anchored to one another. This is achieved by a thread in accordance with the present disclosure which preferably extends from the screw shaft in an uninterrupted manner up to and into the screw head.
Due to the identical pitch of the thread in both regions, that is at the screw shaft and at the screw head, or over the total screw up to the head, the aforesaid compression effects do not occur which can occur in solutions known from the prior art.
It is particularly advantageous for the screw head to have a larger diameter than the screw shaft. If the head diameter of the screw is enlarged with respect to the screw shaft diameter, the screw can first be screwed through the plate into the bone without a connection to the place and only locks when the enlarged screw head in the plate is reached.
An aspect of the present disclosure is particularly preferred in which the screw shaft merges continuously, that is constantly, into the screw head. In a preferred aspect of the present disclosure, the thread extends continuously from the screw shaft up to and into the screw head.
The screw shaft can be cylindrical, for example.
Provision can furthermore be made for the screw head to be designed with a constantly increasing diameter starting from the screw shaft. The shape of the screw head can be any desired one per se. It is, for example, conceivable that the screw head is made conical or similar to a cone, similar to a sphere or in the form of a hemisphere or in the form of other shaped curves. It is generally conceivable to design the screw head with outer sides straight or curved in longitudinal section or also with convex or concave outer sides.
In a preferred aspect of the present disclosure, provision is made for it to be a single-start thread; but multi-start threads can also be realized.
The screw, in particular the screw head, can have a recess for a tool for the turning of the screw. It can, for example, be a recess which is made such that an inner or outer shape-matched connection is maintained with the tool. For example, a recess in the form of a slit, a crossed recess, an inner polygonal recess (e.g. a hexagonal or square recess), a star-shaped or torx-shaped recess are conceivable, as are all other known drive variants. Analogously, an outer shape-matched connection is also conceivable.